1. Field of the Invention
This application claims priority on Patent Application No. 2004-199649 filed in Japan on Jul. 6, 2004, the entire contents of which are hereby incorporated by reference.
The present invention relates to optical transmission devices used in electronic equipment such as DVD players, DVD recorders, televisions, and set-top boxes, as well as audio-video receivers, personal computers, PDAs, mobile phones and the like; and further relates to electronic apparatuses.
2. Description of the Related Art
In recent years, in household equipment of which DVD is representative, digital audio signal transmission by optical signals is becoming widespread. The receiving and transmitting portions of such digital audio signal transmission are provided with a mechanism that, when signal transmission is not performed, prevent the invasion of dust and other foreign substances into the part where the light receiving and transmitting portion is optically/mechanically joined with the plug portion of the fiber-optic cable, and that protect the eyes from light leakage.
As this sort of mechanism, in the conventional technology, shutter mechanisms were used such as a type in which a protective cap is fitted on the insertion portion, and a type in which a cover opens and closes in response to plug insertion and removal. In recent years, many products have been provided with these shutter mechanisms for the sake of convenience and preventing the accidental invasion described above.
Optical transmission devices provided with this type of shutter mechanism include a case that holds an optical element that receives and/or transmits light, the case being provided with a plug insertion hole into which a plug for transmitting an optical signal is inserted; a shutter that opens and closes this plug insertion hole; and a torsion coil spring that biases the shutter in the direction that closes the shutter (for example, see JP 2003-322766A).
In this optical transmission device, when a plug is not inserted, the shutter is biased by the torsion coil spring from the inside of the case towards the outside, and becomes closed. When inserting a plug, the shutter is pushed inside along with this plug insertion. When the plug is fully inserted, the shutter and the torsion coil spring are contained inside the case without harming the optical system of the optical element and the fiber-optic plug (hereinafter, referred to as “plug”). When the plug is removed, there is movement opposite to that when the plug is inserted. That is, the force that lets the torsion coil spring return to its original shape pushes the shutter in the direction outside the case body, and it returns to its original state.
In these conventional optical transmission devices, the case is divided into halves so that it has a front portion housing and a rear portion housing, and when installing the shutter mechanism, the front portion housing must be joined with the rear portion housing after this shutter mechanism is installed inside the front portion housing. Therefore, the assembly structure of the optical transmission device is complicated, and the conventional technology has not arrived at a point where the number of parts can be adequately reduced.